Electrical control circuit



Jan. 11, 1949. P. GLASS ELECTRICAL CONTROL CIRCUIT 2 Sheets-Sheet 1 Filed May 14, 1945 fazf Z/M BS RQ m n Jan. 11, 1949. P. GLASS ELECTRICAL CONTROL CIRCUIT w i fmwi Z m3 Sq M/ N @M 2% W Filed May 14, 1945 Patented Jan. 11, 1949 I ELECTRICAL CONTROL CIRCUIT Paul Glass, Chicago, 111., assignor to Askania Regulator Company, Chicago, 111., a corporation of Illinois Application May 14, 1945, Serial No. 593,738

27 Claims.

1 The invention relates generally to electrical control circuits and more particularly to control circuits wherein a small signal ls utilized to govern substantially larger power application or where the signal is amplified or modified, or both,ior subsequent use in its amplified and/or modified form. v

Heretofore circuits of the character described have depended largely upon electron tubes for accomplishment of the ends sought, necessitating complicated circuits or excessive numbers of stages of amplification with the resultant disadplification or modification, or both, of a signal or for the utilization of a small signal in the control of substantially larger power application.

Another object of the invention is to provide new and improved electrical control circuits adaptable to respond either to alternating current or direct current signals and adaptable to produce either direct or alternating current.

Another object is to provide new and improved electrical control circuits in which the input or controlling circuit is completely separated electrically from the output or controlled circuit and cannot be influenced by the output circuit.

Another object is to provide a new and improved circuit of the character described having an electron tubeless, main amplification or control stage and an input signal circuit in advance of the main stage conditioning the signal by modification and possibly also amplification for use in connection with the main stage.

Still another object is to provide a new and improved control circuit in which the main 'amplification and control means is composed of saturable reactors.

A further object is to provide a control circuit, including saturable reactors, which will function in response to a D. 0. signal to produce an A. C.

output or a D. C. output of a given magnitude independently of the magnitude of the signal but varying in sign with the sign of the signal.

Yet a further object is to provide 'a control circuit, including saturable reactors, which will function in response to an A. C. signal to produce an A. C. output or a D. C. output of a given magnitude independently of the magnitude of the signal but varying in sign with the sign of the 8 8 81.

Other objects and advantages will become 'apparent from the following detailed description taken in connection with the accompanying drawings, in which:

Fig. 1 is a box-type diagrammatic illustration of a circuit embodying the features of this invention.

Fig. 2 is a circuit diagram illustrating in detail a possible construction that the units represented by the rectangles in Fig. 1 may take.

Fig. 3 is a diagram illustrating the character of the output of the first unit of the circuit.

Fig. 4 is a diagram similar to Fig. 3 illustrating the character of the output of the second unit of the circuit.

Fig. 5 is a diagram similar to Fig. 3 illustrating the character of the final output of the circuit.

Fig. 6 is a circuit diagram illustrating another specific form that the units represented by the rectangles of Fig. 1 may take.

Fig. 7 is a diagram illustrating the character of the output of the first unit of Fig. 6.

Fig. 8 is a diagram similar to Fig. 7 illustrating the character of the output of the second unit 0! Fi 6.

Fig. 9 is a diagram similar to Fig. '7 illustrating the character of the output of the third or final unit of Fig. 6.

For purposes of disclosure there is shown in the drawings and will hereinafter be described a general and several specific circuits, being 11- lustrative embodiments of the invention. It is not intended, however, that the invention is to be limited thereby to the specific disclosures made. On the contrary, it is intended to cover all modifications and alternative constructions falling within the spirit and scope of the invention as defined in the appended claims.

Generally speaking, the invention contemplates the provision of a new and improved circuit wherein a small electrical signal is utilized to govern substantially larger power applications or where the signal is amplified or modified, possibly both, for subsequent use in its new form. In such a circuit the input is a controlling signal while the output is a controlled signal regardless of whether the latter is of a magnitude commonly referred to as a signal or is of such magnitude as to be, or is in fact, the operating energy' for'an electrical device such as a motor or the like. To

3 that end, the circuit is composed generally of means for modifying and possibly amplifying the controlling or the controlled signal, and means functioning as the main amplifying or control means.

Herein the general circuit (see Fig. 1) is composed of three subcircuits or circuit units or portions A, B and C. Of these units, A is the main amplifying or control means or circuit and functions to have an output of alternating current controlled as to magnitude and sign by the controlling or input signal, but having an independent power source so that the absolute power output is not limited by the power of the signal source. Unit B is the control signal receiving unit. This unit usually functions to amplify the signal but, above all, it modifies the character of the signal so as first to obtain a signal of a character suitable for use with unit A, and, secondly, to obtain a signal of such character as to result in an output of a character desired. Herein the signal is so modified as to have an on or ofi characteristic, 1. e., the modified signal is either zero or a certain maximum value regardless of the magnitude of the input signal. Unit C is also a modifier of the signal which it receives, though herein the function of unit C is always that of a rectifier converting the A. C. output of unit A to a D. C. output. The term direct current" or its abbreviation D. C., as herein employed to designate the output of the units C and B and the control coils of the unit A, is used in the broad sense of that term, i. e., as opposed to alternating current and as including pulsating current such as produced by a generator or rectifier and not in the limited sense only of absolutely continuous, pulse-free current such as produced by a chemical cell under constant load.

As the description proceeds, it will become apparent that by appropriate construction of the unit B and by use or elimination of the unit C the invention may be employed to respond either to an A. C. or a D. C. input or control signal, while obtaining either an A. C. or a D. C. output. Moreover, by the employment of A. C. or D. C. signal receiving units B of the character hereinafter described, circuits embodying the concept of this invention may be employed to obtain an A. C. output which is either zero or some definite magnitude regardless of the magnitude of the input signal and regardless of whether that be an A. C. ora D. C. signal; and similarly a D. C. output may be obtained which also is either zero or some definite magnitude regardless of the magnitude of the input signal and regardless of whether the same is an A. C. or a D. C. signal. Equally important is the fact that the sign of the output, be it the A. C. output or the D. C. output, is also controlled by the sign of the input or control signal. In other words, the circuit acts as .a reversing switch. The meaning of the term "sign as applied to D. C. signals or output is, of course, the customary meaning and hence will be understood. The meaning herein of the term "sign" as applied to an A. C. signal or output is that of 180 phase displacement. Thus circuits embodying the concept of this'invention may be employed to obtain an A. C. or a D. C. output 'of definite and constant value from a D. C. input signal of varying magnitude; or an A. C. or D. C. output of definite and constant value from an A. C. input signal of varying magnitude, the sign of the output in all instances varying with the sign of the input signal. In

e speaking of A. C. or D. C. currents or outputs, average and effective and not instantaneous values or magnitudes are intended.

Turning now to a consideration of the more detailed embodiments of the invention, the unit A will first be described. This unit, as already stated, is the main amplification stage and control unit or subcircuit and accomplishes control of the magnitude and the sign of the output in accordance with the magnitude and sign of the signal without the employment of electron'tubes. The unit A is the same in all of the circuits disclosed herein and it will thus be described in detail but once in connection with the description of the circuit disclosed in Fig. 2. Referring to Fig. 2, the unit A comprises a pair of saturable reactors represented by the broken-line rectangles IB and I8. The saturable reactor I5 is composed of a pair of A. C. coils I1 and I8 and of a D. C. or control coil l8. All of the coils are wound on a common iron core 20 with coils l1 and I8 opposed so that current flowing in the coils I1 and IE will not induce current or voltage in the D. C. coil l9, while flux produced by direct current flowing in the D. C. coil l9 will vary the impedance of the A. C. coils l1 and it by varying the degree of saturation or the core 20. The reactor is further so designed that the coils i1 and I8 have a very high impedance when no current is flowing in the D. C. coil is. Necessarily the reactor and particularly the coils thereof must be designed with a view to the voltages with which it is to be employed, with the coils I1 and I8 being capable of taking substantially the full applied voltage when no current is flowing in the D. C. coil IS. The saturable reactor i8 is identical with the reactor l5 and comprises A. C. coils 2| and 22 and a D. C. or control coil 23, all wound on a common iron core 24.

The unit A, hereinafter sometimes referred to as the saturable reactor circuit, is completed by an A. C. supply circuit comprising power supply leads 25 and 26 adapted to be connected to an A. C. power source represented at 21, and output leads 28 and 29 terminating in output terminals 80. The A. C. coils of the saturable reactors are so connected in the supply circuit that the output will have a sign depending upon which of the'two reactors is predominating at the time. In other words, the A. C. coils of the saturable reactors are so connected in the supply circuit that when one of the reactors is predominating the output terminals 30 will be connected to the source 21 in one manner, while when the other reactor is predominating the connection of the output terminals so to the source 2'! will just be reversed, thereby bringing about the reversal in sign above mentioned. While this might be accomplished in a variety or ways, the A. C. coils i1 and 2| have one and connected to the power lead 25 by leads 3| and 32, respectively. The coils l8 and 22 of the reactors ill and i6, respectively, have one end connected to the power lead'26 by leads 33 and 34, respectively. The remaining ends of the coils l1 and 2| are by leads 35 and 36 connected, respectively, to the output leads 28 and 29, while the remaining ends of coils l8 and 22 are by leads 31 and 38 connected, respectively, to the output leads 29 and 28. There results in eflect a construction in which the coils l1, l8, 2| and 22 form the legs or a Wheatstone bridge with the power supply leads 26 and 28 being common to the coils l1 and 2| and I8 and 22. respectively, and with the output leads 28 and 28 common to the coils l1 and 22 and i8 and 2|, respectively.

In the embodiment of the invention shown in Fig. 2,; the circuitis adapted to respond to a D. C. input tor control signal.- Accordingly, there is illustrated, by way of example, a unit B which is operable to receive a D. C..signal, amplify the same to a magnitude suitable for use in connection with the saturable reactors l andli, and, at the same time, modify the signal to give it a desired characteristic and cause energization of one or the other of the D. C. coils l9 and 23, depending upon the sign of the input signal, but never both coils simultaneously for any material period of time. Herein the unit B is of such character that an input signal will cause energization of the D. C. coils l9 and 23, as shown in Fig. 3, wherein the line il represents the current flowing in the coil l3 and i2 represents the current flowing in the coil 23. In other words so long as the input signal is and remains zero the current in each of the coils l3 and 23 will also be zero. With an increase in the signal magnitude,

regardless of how small, that is with any signal of a magnitude other than zero, the current in one coil will remain at zero while the current in the other coil will Jump to some definite and constant magnitude as represented in Fig. 3. Which of the coils l9 or 23 will be energized andwhich will remain deenergized will be determined by the sign of the input signal. Note that the unit B as to the individual coils l9 and 23 has an oil or full-on characteristic and as to the unit as a whole has what will result in an output sign controlling characteristic.

While a unit B capable of producing currents in the coils I3 and 23 of the character described might take a variety of forms, one such unit is shown in Fig. 2, it being understood that the showing is exemplary only and that avariety of other subcircuits might be employed and that, in particular, it might prove necessary to have more than one stage to produce the amplification of the signal required to provide direct currents of a magnitude suitable for control of saturable reactors. -Herein the unit 13 or signal input circuit comprises a pair of grid controlled, gaseous tubes 43 and 44 each having a plate 45, a cathode 46 and a grid 41. The tube 43 has a plate circuit, generally designated 48, which includes the D. C. coil IQ of the saturable reactor l5 and the tube 44 has a plate circuit, generally designated 49, which includes the D. C. coil 23 of the saturable reactor IS. A D. C. voltage source, herein shown as a battery 50 common to the two xplate circuits 48 and 49, supplies the ,plate voltage of the tubes. Each of the tubes 43 and 44 has a grid circuit, generally designated 5| and 52, respectively, with each circuit including a resistance 53 and a grid bias voltage source, here shown as a battery 54, common to. the two grid circuits. The D. C. signal input terminals 54 and 55 are connected to the notcommon ends of the resistance 53. Inasmuch as the tubes are of the gaseous type and their plate voltage is supplied by a battery, a tube once fired will continue to fire even though the signal is removed from its grid or made negative. Hence there is connected across the plate circuits of the tubes 43 and 44 a condenser 56 which functions in well known manner to extinguish that one of the tubes which has no positive signal on the grid. It is to .be understood that the tubes 43 and 44 are provided with suitable means for heating the cathodes, though not here shown. This means, of course, that the unit B here described has no neutral or off position, in so far as the signal is concerned, once one of the operation of the circuit as thus far described tubes is caused to fire. The unit is, in effect, therefore, a reversing switch without a neutral or central position. It also means that the tubes will fire simultaneously for that infinitesimal interval of time required for the newly firing tube, acting through the condenser 53, to arrest firing of the other tube.

For ready understanding of this invention, the

will now be set forth. Let it be assumed, therefore, that the input'signal is zero. Under this assumption, no current will be flowing in the coils l9 and 23. There will thus be no change in the impedance ofthe A. C. coils and hence no difierence in potential across the output terminals 30 of the saturable reactor circuit. This is due to the fact' that the output terminals 30 are through leads 23 and 23 connected to points in the energy-supply circuit which are at the same potential. Let it next be assumed that the sign or polarity of the D. C. input signal is such that anincrease in signal magnitude falls to the right of the vertical axis of the graph of Fig. 3. Under those circumstances and independently of the magnitude of the signal, the tube 43 will break down and the current il flowing in the D. C. coil l3 will immediately jump to the definite and constant value represented in Fig. 3, which is the full output of the tube 43, while the current i2 fiowing in the coil 23 will remain at zero. With such fiow of current in the coil I9, the impedance of the A. C. coils l1 and I8 associated therewith will decrease and there will be a correspon'dingly smaller voltage drop across those coils. The impedance of the coils 2| and 22, however, will remain the same with no change in voltage drop across those coils for there has been no change in current in the control coil 23. As a result, with the A. C. coils connected as here shown, there will be a difference of potential between the output terminals 30. This difference of potential between the output terminals 30 will go from zero to some definite and constant value the same as the current in the control coil l9 went from zero to a definite and constant value. The value of the output of the saturable reactor circuit will, of course, be determined by the magnitude of the current flowing in control coil l9 and by the character and size of the A. C. supply source 21 and not by the value of the input signal.

If now it be assumed that the sign or polarity of the input signal is reversed and then increased in magnitude as before, it will be noted that just the opposite occurs. Tube 44 will now break down and simultaneously condenser 58 will extinguish tube 43. The full output current of tube 44, as represented by i2 in Fig. 3, will now fiow in control coil 23, while current in the coil l9 ceases to'fiow. This time the impedance of the coils 2i and 22 of the reactor I6 is decreased while the impedance of the coils l1 and I8 of the reactor I5 is restored to normal. This again produces a difference of potential between the output terminals 30. This potential, however, is of the opposite sign or polarity from that obtained from the condition above assumed. As a consequence, there results a circuit having as best seen in Fig. 4, an alternatin current output, represented by the line 56, which is independent in magnitude of the magnitude of a D. C. input signal and which corresponds in sign to the sign or polarity of the D. C. input signal. Thus the circuit of Fig. 2 so far described results in control similar to that of a reversing switch without a neutral or zero position but obtains that control by means of a D. C. signal. Employed, for example, in connection with a single phase A. C. load, the circuit at initial zero signal would cut oil all power to the load, simulating switch-open condition: once a signal above zerois applied. however. the full output of the circuit is supplied independently of the signal magnitude but with the phase or sign of the A. C. power supplied determined by the sign of'the D. C. signal. This simulates switchclosed condition. In this connection, it is also pointed out that, with the A. C. coils of the saturable reactors so connected as to prevent their inducing any voltage in the associated D. C. coil, the saturable reactor circuit is incapable of infiuencing the signal input circuit and thus reactions of the controlled signal, that is, the output of the saturable reactor circuit, be it of a character to be classified as a signal, or be it the actual power supplied to a load, such as a motor or the like, cannot be reflected back into the signal input circuit.

In the embodiment of the invention shown in Fig. 2, the unit C is connected as the A. C. load of the saturable reactor circuit. Herein, as already stated, the unit C is a rectifier and is, moreover, a rectifier which gives full wave rectified output. Herein the rectifier unit C is composed of four grid controlled, gaseous tubes 80, BI, 82 and 63, each having a plate 84, a cathode 65 and a grid 68. The rectifier is inductively coupled to the saturable reactor circuit through the medium of a transformer T having a primary winding 61 connected to the output terminals 30 and a secondary winding 88. The tubes 80 to 83 are connected to operate in pairs, depending upon the polarity of the output of the saturable reactor circuit. To that end, the plates 64 of the tubes 80 and BI are by leads 69 and I0, respectively. connected to the ends of the secondary winding 68, while the cathodes 65 of the tubes 62 and 63 are by the same leads connected to the ends of the secondary winding 68. The cathodes 85 of the tubes 60 and iii in turn and the plates 64 of the tubes 62 and 63 are by a common lead H connected to a center-tap 12 of the secondary winding 88. The lead l'l actually, of course. is a split lead incorporating therein output terminals 13 to which a D. C. load is intended to be connected. The grid voltages are designed to be either in phase or in counterphase with the output of the saturable reactor circuit, so that one or the other of the pairs of tubes may function, depending upon the sign or phase of the output of the saturable reactor circuit. Accordingly, the grids Bil-of the tubes 60 and Bi are by leads I4 and 15, respectively, connected to the ends of a secondary winding 76 of the transformer 11 having a primary winding 18 adapted to be connected to a suitable A. C. source represented at 19. The midpoint oi the secondary winding 16 is by a lead 80 connected to the common lead H. Potential for the grids 88 or the tubes 82 and 63 is provided respectively by windings Bi and 82 constituting a split secondary of a transformer 83 having a primary winding 84 connected to a suitable A. C. source represented at 85. The remaining ends of the windings I! and 82 are connected, respectively, to the leads 69 and 10. It is to be appreciated that, though not here shown, suitable heating elements are provided for the cathodes of the tubes.

With a rectifier of the character here dis= closed, one of the tubes 60 to 83 will fire during each half cycle of the alternating current output of the saturable reactor circuit. Tubes Oil assess? acter.

and ti will fire, one for the positive. the other for the negative full half cycle when the output of the saturable reactor has one sign, while the tubes 82 and 63 will fire, one for the positive, the other for the negative half cycle when the output of the saturable reactor circuit is of reversed sign. Thus full wave rectified output is obtained at the'output terminals 13 of the rectifier circuit. Since full wave rectified output is obtained, it will be proportional in magnitude to the magnitude of the output of the saturable reactor circuitand hence will have the same off or full-on characteristic. Further, the D. C. output of the rectifier circuit will vary in polarity with the polarity of the input signal and thus there results an output such as represented by the line 8B of Fig. 5, namely, a D. C. output which is either zero so long as the signal is zero, or a definite and constant value independent of the magnitude of the input signalbut corresponding in sign to the sign of the input signal once the signal has any value other than zero.

In Figs. 6 to 9, inclusive, there is disclosed an embodiment of my invention in a circuit responding to or controlled by an A. C. signal. Such a circuit, like the circuit of Fig. 2, may have an A. C. output or a D. C. output. Referring to Fig. 6. the circuit therein disclosed is composed of a saturable reactor circuit A, an input signal amplifying and modifying unit or subcircuit B, and a rectifier unit C. The saturable reactor circuit or the unit A is identical with the unit A shown in Fig. 2. Suffice it to say, therefore, that the unit A is composed of two saturable reactors i5 and i6 and that the reactor i5 has two A. C. coils I1 and i8 and a D. C. or control coil i9, and that the reactor it has two A. C. coils 2i and 22' and a D. C. or control coil 23'. Completing the saturable reactor circuit is a supply circuit having power leads 25' and 26' connected to a source of alternating current power, represented at 21', and output leads 28' and 29'. connected to output terminals 30'. The coils are connected as described in connection with Fig. 2.

Unit B, the signal input circuit, like the unit B of Fig. 2, is adapted to receive the input or control signal, amplify it so as to convert it to a value capable of use with saturable reactors, and modify or condition the signal for use with saturable reactors and to accomplish the end here sought. Such modification in this form of the invention involves conversion of the signal from A. C. to D. C. and further involves modification to result in a signal of appropriate char- Herein the unit B must be such as to result in a current in the D. C. windings l9 and 23' of the character illustrated in Fig. 7 in which, for example ii represents the current in coil l9 and 12 represents the current in coil 23'. In other words, at zero signal, neither coil l9 nor coil 23' should be energized; with a signal,

one or the other of the control coils i9 and 23 should be energized, depending upon the sign of the input signal; but never should both coils be energized simultaneously. Moreover, the magnitude of the current should have a definite and constant value independent of the magnitude of the input signal,

Shown in Fig. 6 for exemplary purposes only, it being understood that a variety of other circuits might be employed and that, in particular, it might be necessary to provide more than a single amplification stage, is one specific embodith refore. that the input signal is zero.

ment that the unit .8 may-take. As, shown in that figure, unit B comprises a pair of grid controlled, gaseous tubes 90 and SI. each having a plate 92, a cathode 93 and a grid M. The tube 90 has a plate circuit, generally designated Bl,

having therein the D. C. coil l'! of the saturable reactor IS. The tube 9| has a plate circuit, generally designated 88, which has connected therein the D. C. coil 23' of the saturable reactor w. The plate circuits of the tubes so and 9| have a common lead 01 adapted for the connectlon therein of an A. C. voltage source, repconnected at'its ends to signal input terminals Hi4 and l05. The midpoint of the secondary juncture of the plateclrcuits with the cathodes. Connectedin the'flad I" is a phase shifting means I01 operable to vary the phase of the grid bias voltage relative to the plate voltage and herein adjusted tobe substantially 180 out of phase with the plate voltage so as to prevent firing of the tubes-when no signal-is present. Connected in the lead from the terminal I to the winding M3 is a condenser I08 provided to give the signal voltage the proper phase relationshinwitli respect to the source for the plate voltage and phase shifting means I01, so that the signal may be effective to control the tubes 80 and SI. A resistor IQB is connected in each of the leads, I00. Though not here shown, it is to be appreciated that the tubes 80 and BI are provided with suitable means for heating the cathodes 93.

- As above stated, the tubes are so biased that at zero signal there is no current flow in either plate circuit. A signal of any value other than zero, making allowance, of course, for a departure suificient to overcome the dead zone of the tubes will cause breakdown of one or the other of the tubes 90 and 9!, depending upon the sign of the signal. Inasmuch as the tubes SI! and BI are gaseous tubes, the magnitude of the signal has no influence on the current flow through the tube where, as here, a signal of the smallest magnitude will cause the tube to break down. Hence there results a D. C. output of the unit B having the characteristic shown in Fig. '7, namely, no current in either coil l9 or 23 at zero signaland a definite and constant value of current in one or the other coil, depending upon the sign of the signal, at any signal above zero magnitude. In Fig. 7, il' represents the current flowing in the coil l9 and i2 represents the curr nt flowing in the coil 23'.

A brief description of the operation of the circuit of Fig. 6, as thus far described, may facilitate understanding of the invention and appreciation of. the advantages thereof. Let it be assumed. Under th-t condition, there will be no flow of current in the T1 C. coils i9 and 23' and no'difierence of po ential between the output terminals because the terminals 30', due to the particular arrangement of the A. C. coils in the supply circuit,

; winding IOI isby'a lead I08 connected to the 10 are connected to points in the circuit normally having the same potential. Let it be assumed further that the A. C. input signal is now increased from zero to some definite magnitude and that the sign of the input signal is such that the signal will lie to the right of the vertical axis of the graph of Fig. 8. Under that assumption, tube 90 will break down and the current il' flowing in the D, C. winding I! will jump from zero to the definite and constant value represented in Fig. 7, this being the full output of the tube 80. The current 11' flowing in the winding 23 will remain zero. Hence the degree to which the core of the saturable reactor I5 is saturated with flux will be varied with a resultant change in the impedance of the A. C. windings of the reactor l5. This will, due to the manner of' connection of the A. C. coils in the supply circuit, produce a voltage differential' between th output terminals 30. Conversely, if the sign of the input signal is reversed and the signal then increased in magnitude asbefore, the tube M will break down and current i2 flowing in the D. C. winding 23' will jump from zero to the definite and constant value represented in Fig. '1, this being the full output of the tube 9|. With such change in sign of the signal, the tube 80 will cease firing and the current il flowing in the winding l9 will return to zero magnitude. Hence the voltage differential between the terminals 30 will be of the same value as previously described, but the sign of the output voltage will be the reverse of that described for the previous condition. It will be apparent, therefore, that there will be obtained an output of the character represented by the line I ill of Fig. 8, namely, an output which is zero at zero signal, but at any other signal magnitude has a single, definite value, with the sign of the output determined by the sign of the input signal. This circuit'thus has output of the same character as is obtained by the corresponding portion of the circuit of Fig. 2, but with control by an A, C. signal rather than by a D. C. signal. The circuit results in control similar to that of a reversing switch but obtains that control by means of an A. C. signal.

The final output of the circuit of Fig. 6 is a D. C. output of a value'zero, or some definite and constant value independent of the magnitude of the input signal but witha sign or polarity corresponding to the sign of the A. C. input signal. To that end, a rectifier circuit or unit C is connected as the load of the saturable reactor circult or unit A. The unit C is identical with the unit C of Fig. 2. Sufilce it to say, therefore, that the rectifier C comprises four grid controlled, gaseous electron tubes 6|, 62 and 63, each tube having a plate N, a cathode 65' and a grid 66'. The rectifier C is inductively coupled to the saturable reactor circuit A through the medium of a transformer T having a primary winding 81' connected to the output terminals 30 of the saturable-reactor circuit and a secondary winding 68. Plate voltages are obtained by connection of the plates'of the tubes 60 to 53 to the ends or midpoints oi the secondary winding 68', while grid.voltages are obtained from suitable A, C. sources represented at 19' and 85' with the grid voltages either in phase or in counterphase with the output-of the saturable reactor circuit A'. The tubes are so connected that they operate in pairs, one pair functioning when the output of the saturable reactor circuit is of one sign, the other pair functioning when the amass? output of the saturable reactor circuit is of rea as more particularly described above.

With this full wave rectification, the D; C. output of the circuit will correspond to the A. C. output of the saturable reactor circuit and, inas-' much as this latter output has already been shown to be of an oil or full-on type and independent oi the magnitude of the A. C. signal (see Fig. 8), the D. C. or end output of the entire circuit will also be 01' an ofl or full-on type and independent of the magnitude of the A. C. input signal. Further, with the sign of the output of each unit corresponding and controlled by the sign of the input to each unit, the D. C. or end output of the entire circuit will also correspond to the sign of the A. C. input signal. Accordingly, there results an output of the character represented by the line HI Fig. 9.

I claim as my invention: I

1. An electrical control circuit comprising a signal input circuit having two sets of output terminals and operable with a signal of any magnitude present to produce at one or the other only oi' the sets of terminals a direct current of constant magnitude larger than zero and. independent of the signal magnitude; the set of output terminals at which current is produced being determined by the sign of the input signal, a saturable reactor circuit comprising a pair of saturable reactors each having an A. C. coil and a control coil, said control coils being. connected one to each set oi output terminals of said input circuit, and an A. C. supply circuit for an A. C. load, the A. C. coils of said reactors being connected in the supply circuit, and a rectifier-circuit, connected to form the load for said supply circuit, including a pair of parallelly connected, alternately operating rectifiers and output terminals for the connection of a D. C. load thereto.

2. An electrical control circuit comprising a signal input circuit having two sets of output terminals and operable to produce at one or the other only of the sets of terminals a direct current of constant magnitude larger than zero and independent oi! signal magnitude, the set of output terminals at which current is produced being determined by the sign of the input signal,

' a saturable reactor circuit comprising a pair of saturable reactors each having a pair of A. C. coils and a control coil wound on a common core, the A C. coils being so arranged as not to. induce an A. C. voltage in the associated control coil, said control coils being connected one to each set of output terminals of said input circuit and an A. C. supply circuit for an A. 0. load, the A. C. coils of said reactors being connected in the supply circuit to form with the load separate circuits each including the A. C. coils of one reactor reversely connecting the load in said supply circuit, and a rectifier circuit connected to form the load for said supply circuit and having output terminals for the connection of a D. C. load thereto, said rectifier circuit including recti'fying means alternately operative in accordance with the phase of the output of said saturable reactor circuit to. vary the sign of its output in accordance with the sign of the input signal.

3. An electrical control circuit comprising a signal input circuit having two sets of output terminals and operable to produce at one or the other only of the sets of terminals a direct current of constant magnitude larger than zero and independent of signal magnitude, the Set 01 cutput terminals at which current is produced being determined by the sign of the input signal, a saturable reactor circuit comprising a pair of saturable reactors each having a pair of A. C. coils and a control coil wound on a common core, the A. C, coils being so arranged as not to induce an A. C. voltage in the associated control coil, said control coils being connected one to each set of output terminals of said input circuit and an A. C. supply circuit for an A. C. load, the four A. C. coils of said reactors being connected in the supply circuit in a manner such that each forms one leg of a Wheatstone bridge, and that the'A. C. coils of each reactor form diametrically opposed legs of the bridge, and a rectifier circuit connected to form the load for said supply circuit and having output terminals for the connection of a D. C. load thereto, said rectifier circuit including rectifying means alternately operative in accordance with the phase of the output of said saturable reactor circuit to vary the sign of its output in accordance with the sign of the input signal.

4. An electrical control circuit comprising a signal input circuit having two sets of output terminals and operable at zero signal to produce a direct current of zero magnitude at both sets of output terminals and operable at any signal magnitude other than zero to produce at one or the other only of the sets of terminals a direct current of constant magnitude larger than zero and independent of signal magnitude, the set flers connected to form the load for saidsupply. circuit, said rectifiers being connected for alternate operation and having common output terminals for the connection of a D. C. load thereto.

5. An electrical control circuit comprising a signal input circuit having two sets of output terminals and operable at zero signal to produce a direct current of zero magnitude at both sets of output terminals and operable at any signal magnitude other than zero to produce at one or the other only of the sets 01 terminals a direct current of constant magnitude larger than zero and independent of signal magnitude, the set of output terminalsat which current is produced being determined by the sign of the input signal, a saturable reactor circuit comprising a pair of saturable reactors each having a pair of A. C. coils and a control coil wound on a common core, the A. C. coils bein so arranged as not to induce an A. C. voltage in the associated control coil, said control coils being connected one to each set of output terminals of said input circult and an A. C. supply circuit for an A. C. load. the A. C. coils of said reactors being connected in said supply circuit in a bridge network with the load and the source of said supply circuit, and a rectifier circuit comprising an inductive coupling having a primary winding connected as the load in said supply circuit and a center-tapped secondary winding, two pairs of grid controlled, gaseous electron tubes and means providing grid voltages for the tubes in phase or in counterphasewith the platevoltages of said tubes, said tubes being connected to provide rectified current or a polarity determined by the sign of the output current of the saturable reactor circuit.

6. A electrical control circuit comprising a signal input circuit having two sets of output terminals and operable at zero signal to produce a direct current of zero magnitude at both sets of output terminals and operable at any signal magnitude other than zero to produce at one or the other only of the sets of terminals 9. direct current of constant magnitude larger than zero and independent of signal magnitude, the set of output terminals at which current is produced being determined by the sign of the input signal, a saturable reactor circuit comprising a pair of saturable reactors each having a pair of A. C. coils and a D. C. coil wound on a common core, the A. C. coils being so arranged as not to induce an A. C. voltage in the associated D. C. coil, said D. C. coils being connected one to each set of output terminals of said input circuit and an A. C. supply circuit for an A. C. load, the four A. C. coils of said reactors being connected in the supply circuit in a manner such that each forms one leg of a Wheatstone bridge, and that the A. C. coils of each reactor are in series when there is an unbalance oi the bridge, and a rectifier circuit comprising an inductive coupling having a primary winding connected as the load in said supply circuit and a center-tapped secondary winding, two pairs of grid controlled, gaseous electron tubes, one pair of said tubes having its plates connected to the ends of said secondary winding and its cathodes connected to the center-tap on said secondary, and the other pair having its plates connected to the center-tap and the cathodes connected to the ends of said secondary winding, and means providing grid voltages for said tubes keeping the grid voltages of one pair of tubes in phase and the grid voltages of the other pair of tubes in counterphase with their respective plate voltages.

'7. In an electrical control circuit, a signal input circuit having two sets of output terminals and operable to produce at one or the other only of the sets of terminals a direct current of constant magnitude larger than zero and independent of signal magnitude, the set of output terminals at which current is produced being determined by the sign of the input signal, and a saturable reactor circuit comprising a pair of saturable reactors each having a D. C. coil and an A. C. coil, and an alternating current supply circuit adapted to have an A. C. load connected therein, the D. C. coils of said reactors being connected one to each set of output terminals of said signal input circuit and said A. C. coils being connected in said supply circuit to produce an alternatin current in the load which is of a constant value larger than zero and independent of signal magnitude but of a sign varying with the sign of the input signal. 7

8. In an electrical control circuit, a signal input circuit having two sets of output terminals and operable witi': a signal of any magnitude present to produce at one or the other only of the sets of terminals a direct current of constant magnitude larger than zero and independent of signal magnitude, the set of output terminals at which current is produced being determined by the sign of the input signal and a saturable reactor circuit comprising a pair of saturable reactors each having a pair of A. C. coils and a D. C. coil wound on a common core, the A. C. coils being so arranged as not to induce an A. C. voltage in the associated D. C. coil, said D. C. coils bein connected one to each set of output terminals of said input circuit and an A. C. supply circuit for an A. C. load, the A. C. coils of said reactors being connected in the supply circuit.to form with the load separate circuits each including the A. C. coils of one reactor reversely connecting the load in said supply circuit.

9. In an electrical control circuit, a signal input circuit having two sets of output terminals and operable to produce at one or the other only of the sets of terminals a direct current of constant magnitude larger than zero and independent of signal magnitude, the .set of output terminals at which current is produced being determined by the sign of the input signal, and a saturable reactor circuit comprising a pair of saturable reactors each having a pair of A. C. coils and a D. C. coil wound on a common core, the A. C. coils being so arranged as not to induce an A. C. voltage in the associated D. C. coil, said D. C. coils being connected one to each set of output terminals of said input circuit and an A. C. supply circuit for an A. C. load, the four A. C. coils of said reactors being connected in the supply circuit each to form one leg of a Wheatstone bridge.

10. In an electrical control circuit, a signal input circuit having two sets of output terminals and operable with a signal of any magnitude present to produce at one or the other only of the sets of terminals a direct current of constant magnitude larger than zero and independent of signal magnitude, the set of output terminals at which current is produced being determined by the sign of the input signal, and a saturablereactor circuit comprising a pair of saturable reactors each having a pair of A. C. coils and a D C. coil wound on a common core, the A. C. coils being so arranged as not to induce an A. C. voltage in the associated D. C. coils, said D. C. coils being connected one to each set of outputterminals of said input circuit, and an A. C. supply circuit for an A. C. load, the four A. C. coils of said reactors being connected in the supply circuit in a manner such that each forms one leg of a Wheatstone bridge and that the A. C. coils of each reactor are connected in diametrically opposed legs of the bridge.

11. In an electrical control circuit a D. C. signal input circuit having two sets of output terminals and operable so long as the signal remains zero to produce a direct current of zero magnitude at both sets of output terminals and operable once a signal of a magnitude other than zero is applied to produce at one or the other only of the sets of terminals a direct current of constant magnitude larger than zero and wholly independent of signal magnitude, the set of output terminals at which current is produced being determined by the sign of the input signal, and a saturable reactor circuit comprising a pair of saturable reactors each having a D. C. coil and an A. C. coil, and an alternating current supply circuit adapted to have an A. C. load connected therein, the D. C. coils of said reactors being connected one to each set of output terminals of said signal input circuit and said A. C. coils being connected in said supply circuit to produce an alternating current in the load which is zero so long as the signal remains zero and of a constant value larger than zero and independent of signal magnitude but of a sign varying with the sign of the input signal once a signal of any magnitude has been applied.

12. In an electrical control circuit, a. D. C.

age source, a common signal input circuit comprising a pair of grid controlled, gaseous electron tubes each having a plate, a cathode and a grid, a common plate voltage source, a common grid bias means biasing said tubes to prevent initial breakdown in the absence of a signal, a plate circuit for each of said tubes, 8. grid circuit for each of said tubes and means for extinguishing one tube upon firing of the other tube and a saturable reactor circuit comprising a pair of saturable reactors each having a pair 01 A. C. coils and a D. C. coil wound on a common core, the A. C. coils being so arranged as not to induce an A. C. voltage in the associated D. C. coil. said D. C. coils being connected one in the plate circuit of each or the tubes in said input circuit and an A. C. supply circuit having output terminals for the connection o! a load therein, the A. C. coils of said reactors being connected in said supply circuit in a bridge network with'the output terminals and the source of said supply circuit.

13. In an electrical control circuit, a D. 0. signal input circuit comprising a pair of grid controlled, gaseous electron tubes each having a plate, a cathode and a grid, a common plate voltage source, a common grid bias means biasing said tubes to prevent initial breakdown in the absence of a signal, a plate circuit for each of said tubes, a grid circuit for each of said tubes and means for extinguishing one tube upon firing of the other tube comprising a condenser connected across the plates of said tubes and a saturable reactor circuit comprising a pair of saturable reactors each having a pair of A. C. coils and a D. C. coil wound on a common core, the A. C. coils being so arranged as not to induce an A. C. voltage in the associated D. C. coil, said D. C. coils being connected one in the plate circuit of each of the tubes in said input circuit and an A. C. supply circuit having output terminals for the connection of a load therein, the A. C. coils of said reactors being connected in said supply circuit in a bridge network with the output terminals and the sourceof said supply circuit.

14. In an electrical control circuit. a D. C. signal input circuit comprising a pair of grid controlled. gaseous electron tubes each having a plate, a cathode and a grid, a common plate voltgrid bias'means biasing said tubes to prevent initial breakdown in the absence of a signal, a plate circuit for each of said tubes, a grid circuit for each of said tubes and means for extinguishing one tube upon firing oi. the other tube, and a saturable reactor circuit comprising a pair of saturable reactors each having a.pair oi! A. C. coils and a D. C. coil wound on a common core. the A. C. coils being so arranged as not to induce an A C. voltage in the associated D. C. coihsaid D. C. coils being connected one in the plate circuit of each of the tubes in said input circuit and an A. 0. supply circuit, the A. C. coils of said reactors being connected in said supply circuit in a manner such that each forms one leg of a bridge network with the A. C. coils oi. each reactor connected in diametrically opposed legs of the bridge network.

15. An electrical control circuit comprising a D. C. signal input circuit comprising a pair of grid controlled, gaseous electron tubes each having a plate, a cathode and a grid. a common plate voltage source. a common grid bias means biasing said tubes to prevent initial breakdown in the absence of a signal, a plate circuit for each oi said tubes, a grid circuit for each of said tubes and means for extinguishing one tube upon firing of the other tube, a saturable reactor circuit comprising'a pair of saturable reactors each having a pair of A. C. coils and a D. C. coil wound on a common core, the A. C. coils being so arranged as not to induce an A. C. voltage in the associated D. C. coil, said D. C. coils being connected one in the plate circuit of each of the tubes'in said input circuit and an A. C. supply circuit having output terminals for the connection of a load therein, the A. C. coils of said reactors being connected in said supply circuit in a bridge network with the output terminals and the source of said supply circuit, and a, rectifier circuit connected to form the load for said supply circuit and having output terminals for the connection of a D. C. load thereto, said-rectifier circuit including rectifying means alternately operative in accordance with the phase of the output of said saturable reactor circuit to vary the sign of its output in accordance with the sign of the input signal.

16. An electrical control circuit comprising a D. C. signal input circuit comprising a pair of grid controlled, gaseous electron tubes each having a plate, a cathode and a grid, a common plate voltage source, a common grid bias means biasing said tubes to prevent initial breakdown in the absence of a signal, a plate circuit for each of said tubes, 9. grid circuit for each of said tubes and means for extinguishing one tube upon firing oi the other tube, a saturable reactor circuit comprising a pair of saturable reactors each having a pair of A. C. coils and a D. C. coil wound on a common core, the AC. coils being so arranged as not to induce an A. C. voltage in the associated D. C. coil, said D. C. coils being connected one in the plate circuit of each of the tubes in said input circuit and an A. C. supply circuit, the A. C. coils of said reactors being connected in said supply circuit in a manner such that each forms one leg of a bridge network with the A. C. coils of each reactor connected in diametrically opposed legs of the bridge network, and arectifier circuit comprising an inductive coupling having a primary winding connected as the load in said supply circuit and a center-tapped secondary winding, two pairs of grid controlled, gaseous electron tubes and means providing grid voltages for the tubes in phase or in counterphase with the plate voltages of said tubes, said tubes being connected to provide rectified current of a. polarity determined by the sign or the output current of the saturable reactor circuit.

17. In an electrical control circuit, an A. C. signal input circuit having two sets of output terminals and operable at zero signal to produce a direct current of. zero magnitude at both sets of output terminals and operable at any signal magnitude other than zero to produce at one or the other only of the sets of terminals a direct current of constant magnitude larger than zero and independent of signal magnitude, the set of output terminals at which current is produced being determined by the sign of the input signal, and asaturable reactor circuit comprising a pair of saturable reactors each having a D. C. coil and an A. C. coil, an alternatingcurrent supply circuit, and an A. C. load connected therein, the D. C. coils of said reactors being connected one to each set of output terminals of said signal input circuit and saidA. C. coils being connected in said supply circuit to produce an alternating current in the load which is zero at zero signal 17 and of a constant value larger than zero and independent of signal magnitude at any magnitude other than zero but of a sign varying with the sign of the input signal.

18. In an electrical control circuit, an A. C. signal input circuit having two sets of output terminals and operable at zero signal to produce a direct current of zero magnitude at both sets of output terminals and operable at any signal magnitude other than zero to produce at one or the other only of the sets of terminals a direct current of constant magnitude larger than zero and independent of signal magnitude, the set of output terminals at which current is produced being determined by the sign or the input signal, and a saturable reactor circuit comprising a pair of saturable reactors each having a pair 01 A. C. coils, and a D. C. coil wound on a common core, the A. C. coils being so arranged as not to induce an A. C. voltage in the associated D. C. coil, said D. C. coils being connected one to each set of output terminals of said input circuit and an A. C. supply circuit having output connections for an A. C. load, the A. C. coils of said reactors being connected in the supply circuit to form with the load output connections separate circuits each including the A. C. coils of one reactor reversely connecting the output connections in said supply circuit.

19. In an electrical control circuit, an A. C. signal input circuit comprising a pair of grid controlled, gaseous electron tubes each having a plate, a cathode and a grid, a plate circuit for each of said tubes including a common A. C.

source of plate potential, a grid circuit for each or said tubes including an A. C. bias operable to bias said tubes to cut off at zero signal magnitude and to fire upon application of a signal, and a saturable reactor circuit comprising a pair of saturable reactors each having a pair of A. C. coils and a D. C. coil wound on a common core, the A. C. coils being so arranged as not to induce an A. C. voltage in the associated D. C. coil, said D. C. coils being connected one in the plate circuit of each of said tubes and an A. C. supply circuit having output terminals for the connection of a load therein, the A. C. coils of said reactors being connected in the supply circuit to form with the output terminals separate-circuits each including the A. C. coils of one reactor reversely connecting the output terminals in said supply circuit.

20. In an electrical control circuit, an A. C. signal input circuit comprising a pair of grid controlled, gaseous electron tubes each having a plate, a cathode and a grid, a plate circuit for each of said tubes including a common A. C. source of plate potential, a grid circuit for each of said tubes including a phase shifter providing the grid bias for said tubes adjusted to cause firing of a tube upon application of a signal of any magnitude and to arrest firing upon removal of the signal, and a saturable reactor circuit comprising a pair of saturable reactors each having a pair of A. C. coils and a D. C. coil wound on a common core, the A. C. coils being so arranged as not to induce an A. C. voltage in the associated D. C. coil, said D. C. coils being connected one in the plate circuit of each of said tubes and an A. C. supply circuit having output terminals for the connection of a load therein, the A. C. coils of said reactors being connected in the supply circuit to form with the output terminals separate circuits each including the A. C. coils of one reactor reversely connecting the output terminals in said supply circuit.

21. In an electrical control circuit, an A. C. signal input circuit comprising a pair of grid controlled, gaseous electron tubes each having a plate, a cathode and a grid, a plate circuit for each of said tubes including a common A. C. source of plate potential, and an inductively coupled signal input means having a primary winding, a secondary winding, the secondary winding being connected at its ends to the grids of said tubes, a phase shifter providing the grid bias for said tubes adjusted to cause firing of a tube upon application of a signaLcf any magnitude and to arrest firing upon removal of the signal and a condenser connected in series with said primary winding, and a saturable reactor circuit comprising a pair of saturable reactors each having a pair of A. C. coils and a D. C. coil said tubes and an A. C. supply circuit having output terminals for the connection of a load therein,

, the A. C. coils of said reactors being connected in the supply circuit to form with the output terminals separate circuits each including the A. C. coils of one reactor reversely connecting the output terminals in said supply circuit.

7 22. An electrical control circuit comprising an A. C. signal input circuit having two sets of output terminals and operable at zero signal to produce a direct current of zero magnitude at both sets 01. output terminals and operable at any signal magnitude other than zero to produce at one or the other only of the sets of terminals 9. direct current of constant magnitude larger than zero and independent of signal magnitude, the set of output terminals at which current is produced being determined by the sign of the input signal, a. saturable reactor circuit comprising a pair of saturable reactors each having a pair'of A. C. coils, and a D. C. coil wound on a common core, the A. C. coils being so arranged as not to induce an A. C.'voltage in the associated D. C. coil, said D. C. coils being connected one to each set of output terminals of said input circuit and an A. C. supply circuit for an A. C. load, the A. C. coils of said reactors being connected in the supply circuit to form with the load separate circuits each including the A. C. coils of one reactor reversely connecting the load in said supply circuit, and a rectifier circuit, connected to form the load for said supply circuit, including a pair of parallelly connected alternately operating rectiflers and output terminals for the connection of a D. C. load thereto.

23. An electrical control circuit comprising an A. C. signal input circuit comprising a pair of grid controlled, gaseous electron tubes each having a plate, a cathode and a grid, a plate circuit for each of said tubes including a common A. C. source of plate potential, a grid circuit for each of said tubes including an A. C. bias operable to bias said tubes to cut of! at zero signal magnitude and to tire upon application of a signal, a saturable reactor circuit comprising a pair of saturable reactors each having a p r of A. C. coils and a D. C. coil wound on a common core, the A. C. coils being so arranged as not to induce an A. C. voltage in the associated D. C. coil, said D. C. coils being connected one in the plate circuit or each of said tubes and an A. C. supply circuit adapted for connection of a load therein, the A. C. coils of said reactors being connected in the supply circuit to form with the load separate circuits each including the A. C. coils of one reactor reversely connecting the load in said supply circuit, and a rectifier circuit connected to form the load for said supply circuit and having output terminals for the connection of a D. C. load thereto, said rectifier circuit including rectifying means alternately operative in accordance with the phase of the output of said saturable reactor circuit to vary the sign of its output in accordance with the sign of the input signal.

24. An electrical control circuit comprising an A. C. signal input circuit comprising a pair of grid controlled, gaseous electron tubes each having a plate, a cathode and a grid, a plate circuit for eachv of said tubes including a only of the sets of terminals a direct current of common A. C. source of plate potential, and

an inductively, coupled signal input means having a primary winding, a secondary winding, the secondary winding being connected at its ends to the grids of said tubes, a phase shifter providing the grid bias for said tubes adjusted to cause firing of a tube upon application of a signal of any magnitude and to arrest firing upon removal of the signal and a condenser connected in series with said primary Winding, a saturable reactor circuit comprising a pair of saturable reactors each having a pair of A. C. coils and a D. C. coil wound on a common core, the A. C. coils being so arranged as not to induce an A. C. voltage in the associated D. C. coil, said D. C. coils being connected one in the plate circuit of each of said tubes and an A. C. supply circuit adapted for connection of a load therein, the A. C. coils of said reactors being connected in the supply circuit to form with the load separate circuits each including the A. C. coils of one reactor reversely'connecting the load in said supply circuit, and a rectifier circuit connected to form the load for said supply circuit and having output terminals for the connection of a D. C. load thereto, said rectifier circuit including rectifying means alternately operative in accordance with the phase of the output of said saturable reactor circuit to vary the sign of its output in accordance with the sign of the input signal.

25. An electrical control circuit comprising a signal input circuit having two sets of output terminals and functioning, once placed in operation, to produce at one or the other only of the sets of terminals a direct current of constant magnitude larger than zero and independent of signal magnitude, the set of output terminals at which current is produced being determined by the sign of the input signal, a saturable reactor circuit comprising a pair of saturable reactors each having an A. C. coil and a D. C. coil, said D. C. coils being connected one to each set of output terminals of said input circuit, and an A C. supply circuit for an A. C. load, the A. C. coils of said reactors being connected in the supply circuit, and a pair of full wave rectifiers connected to form the load fpr said supply circuit,

. said rectifiers being connected for alternate operation and having common output terminals for the connection of a D. C. load thereto.

constant magnitude larger than zero and wholly independent of signal magnitude, the set of output terminals at which current is produced being determined by the sign of the input signal, a saturable reactor circuit comprising a pair of saturable reactors each having a pair of A. C. coils and a control coil wound on a common core, the A. C. coils being so arranged as not to induce an A. C. voltage in the associated control coil, said control coils being connected one to each set of output terminals of said input circuit and an A. C. supply circuit for an A. C. load, the A. C. coils of said reactors being connected in said supply circuit in a bridge network with the load and the source of said supply circuit, and a rectifier circuit comprising an inductive coupling having a primary winding connected as the load in said supply circuit and a center-tapped secondary winding, two pairs of grid controlled gaseous electron tubes and means providing grid voltages for the tubes in. phase or in counterphase with the plate voltages of said tubes, said tubes being connected to provide rectified current of a polarity determined by the sign of the output current of the saturable reactor circuit.

27. In an electrical control circuit, a signal input circuit having two sets of output terminals, gaseous electron discharge devices governing the output at said terminals, and means for controlling said devices rendering the same operable to produce at one or the other only of the sets of terminals a direct current of constant magnitude larger than zero and independent of signal magnitude, the set of output terminals at which current is produced being determined bythe sign of the input signal, and a saturable reactor circuit comprising a pair of saturable reactors each having a D. C. coil and an A. C. coil, and an alternating current supply circuit adapted to have an A. C. load connected therein, the D. C. coils of said reactors being connected one to each set of output terminals of said signal input circuit and said A. C. coils being connected in said supply circuit to produce an alternating current in the load which is of a constant value larger than zero and independent of signal magnitude but of a sign varying with the sign of the input signal.

PAUL GLASS.

REFERENCES ;CITED The following references are of recordlin the file of this patent:

UNITED STATES PATENTS Number Name Date 1,678,965 Von Bronk July 31, 1928 1,844,704 Thompson Feb. 9, 1932 2,085,595 Livingston June 29, 1937 2,276,752 Willis Mar. 17, 1942 

